Microlithography is used for the production of microstructured components such as for example integrated circuits or LCDs. The microlithography process is carried out in what is referred to as a projection exposure apparatus having an illumination system and a projection objective. The image of a mask illuminated via the illumination system (=reticle) is in that case projected via the projection objective on to a substrate (for example a silicon wafer) which is coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection objective to transfer the mask structure on to the light-sensitive coating of the substrate.
Retardation elements are frequently used both in the illumination system and also in the projection objective in order for example to afford defined polarisation distributions or to specifically manipulate polarisation distributions. Examples in that respect are for example the use of lambda/2-plates or the specific compensation of an unwanted disturbance in polarisation distribution, which is caused by the retardation in one or more lenses of intrinsically or naturally birefringent material. The term ‘retardation’ is used to denote the difference in the optical paths of two orthogonal (mutually perpendicular) polarisation states.